Field
The disclosed aspects relate generally to communications between devices and specifically to methods and systems for improving remote near field communication (NFC) device detection through use of an oscillator circuit connected to an NFC antenna and matching network.
Background
Advances in technology have resulted in smaller and more powerful personal computing devices. For example, there currently exist a variety of portable personal computing devices, including wireless computing devices, such as portable wireless telephones, personal digital assistants (PDAs) and paging devices that are each small, lightweight, and can be easily carried by users. More specifically, the portable wireless telephones, for example, further include cellular telephones that communicate voice and data packets over wireless networks. Many such cellular telephones are manufactured with ever increasing computing capabilities, and as such, are becoming tantamount to small personal computers and hand-held PDAs. Further, such devices are enabling communications using a variety of frequencies and applicable coverage areas, such as cellular communications, wireless local area network (WLAN) communications, NFC, etc.
When using NFC, it is desirable for a poller device to be able to detect the proximity of a listener device (e.g., a passive tag, an active device functioning as a passive tag, etc.) using as little power as possible. Power is a particular concern since, in typical applications, the poller device spends most of its time in the listening mode (cycling between listen and sleep with some duty cycle).
Currently, the poller device may fully activated (TX+RX antennas) for transmission of a carrier signal and listening for a load modulation response. Alternatively, the poller device may activate the TX antenna and monitor the power consumption, and/or the poller device may activate the TX antenna and monitor power consumption over a frequency sweep. In this case, remote NFC device detection may be based on a comparison on the oscillator frequency to a known frequency reference. When an NFC reader chip is integrated in a wireless communications device (WCD), it may use a dedicated crystal oscillator or share a crystal oscillator with other chips and subsystems. A high quality crystal oscillator may provide a high quality reference signal, but also may consume a significantly high current. Currently, a NFC chip may periodically wake up from a sleep state to perform tag detection. In such an aspect, the NFC chip may use either a shared system low power reference clock, or an integrated low crystal-less low power oscillator (LPO), to measure time between wake ups. Thereafter, the NFC chip may turn on the high quality crystal oscillator for the remote NFC device detection. As such, the impact of the crystal oscillator to average power consumption may be calculated as the power used by the crystal oscillator multiplied by the detection time and divided by the wake up interval.
Thus, improved apparatuses and methods providing mechanisms for detecting a remote NFC device without excessive power consumption may be desired.